1. Field of the Invention
The present invention relates to a method of sealing an electric wire-connecting portion formed by connecting together conductive ends of a plurality of electric wires, in which electric insulation and waterproofing property of the electric wire-connecting portion are secured by covering the electric wire-connecting portion. Furthermore, the present invention also relates to a tool for holding a heat shrinkable tube used in the sealing method, and a tube shrinking machine for heating a heat shrinkable tube covering the electric wire-connecting portion.
The present application is based on Japanese Patent Application No. Hei. 9-342971, which is incorporated herein by reference.
2. Description of the Related Art
An example of a method of protecting an electric wire-connecting portion in which conductive ends of electric wires are bundled and connected to each other, will be described with reference to FIGS. 9 through 11.
In FIG. 9, conductive ends of a plurality of electric wires W are bundled and connected together to form an electric wire-connecting portion 1. The electric wire-connecting portion 1 is subjected to thermal press fitting so that an end portion 1a is formed. Further, the electric wire-connecting portion 1 is subjected to bonding treatment (not shown) in which an adhesive is penetrated into or is applied onto the electric wire-connecting portion 1 so as to secure its waterproofing property.
The electric wire-connecting portion 1 is covered by a heat shrinkable tube 3. One end of the heat shrinkable tube 3 is sealed with a hot melt adhesive 2. Further, the heat shrinkable tube 3 is filled with sealing compound such as butyl rubber.
The electric wire-connecting portion 1 thus covered with the heat shrinkable tube 3 is inserted into a tube shrinking machine 5 in a direction of an arrow as shown in FIG. 10.
A space 5a is formed in the body of the tube shrinking machine 5. As shown in FIG. 10, the space 5a extends in a slit-like manner over from a front end 5b of the tube shrinking machine 5 to one side 5c of the tube shrinking machine 5. The electric wire-connecting portion 1 covered with the heat shrinkable tube 3 is passed through the space 5a of the tube shrinking machine 5. A wire transporting section 6 includes a pair of an upper transport belt 6a and a lower transport belt 6b, which are disposed in the space 5a at the upper and lower portions adjacent to the one side 5c. The transport belts 6a and 6b transport a bundled portion of the electric wires W while holding it therebetween. The wire transporting section 6 is driven by a motor (not shown).
FIG. 11 is a cross sectional view taken along a line XI--XI in FIG. 10. As shown in FIG. 11, a pair of heaters 7 are disposed inside of the tube shrinking machine 5 to sandwich the space 5a. The heaters 7 are used for heating the heat shrinkable tube 3 so as to shrink. The electric wire-connecting portion 1 with the heat shrinkable tube 3 is inserted into the tube shrinking machine 5, and is transported by the transport belts 6a and 6b while the bundled portion of the electric wires W is held therebetween. During the transportation, the heat shrinkable tube 3 is heated by the heaters 7. In accordance with the heating, the heat shrinkable tube 3 shrinks to hermetically seal the electric wire-connecting portion 1 as shown in FIG. 9. As a result, electrical insulation and waterproofing property of the electric wire-connecting portion 1 are ensured, and the electric wire-connecting portion 1 is taken out of the tube shrinking machine 5.
In the above tube shrinking machine 5, however, when the electric wire-connecting portion 1 is transported while the bundled portion of the electric wires W is held between the transport belts 6a and 6b, the electric wire-connecting portion 1 may vibrate in the arrow directions as shown in FIG. 11. As a result, there is a possibility in that the heat shrinkable tube 3 is disengaged from the electric wire-connecting portion 1.
Further, there is a possibility in that the heat shrinkable tube 3 is brought into contact with the heater 7, and therefore it burns.
Furthermore, when the heat shrinkable tube 3 vibrates and the end of the heat shrinkable tube 3 sealed with the hot melt adhesive 2 is too close to the heaters 7, the hot melt adhesive 2 melts and flows out of the end of the tube as shown in FIG. 12. The result is to destroy the structure for securing the electric insulation and the waterproofing property of the electric wire-connecting portion 1.